I don't think you are going to find a wiper motor that will work on your truck, without some type of modification, at a place like Summit. All the modern wipers have both wipers going the same direction at the same time, or they will power only one wiper, which would require 2 motors to run both wipers. The wipers on your truck run in opposite directions, they open going away from each other and close going towards each other. To do that with a modern system, you would need to set up an idler to change the direction of one of the wipers. It can be done, but will require some creative work, or you will have to modify the wiper set up on your truck, or run with only one wiper.

The only other option you may have is to check out specialty equipment offerings. I have noticed that www.robertsmotorparts.com lists a replacement 12 volt wiper motor, its not cheap and requires special wiper arms, but may be a good option. They have had the same wiper system in their books for a long time, it must work pretty well, but I have not done a wiper motor with Roberts. I have purchased weatherstripping from them in the past, and the person I spoke with had a very good knowledge of these old Dodge/Fargo trucks. I would contact them to hear what they have to say. Gene